What Green Roofs Actually Do?

Green roofs do an excellent job of insulating a building
from heat, cold, and noise. They trap a much greater amount of precipitation
than conventional roofs, and this reduces the amount of runoff they contribute
to municipal drainage systems during heavy storms. When they're built properly,
green roofs can even be a viable area for growing crops such as vegetables.

Assessing A Roof's Capacity

Green roofs can be designed to fit many different
conditions. The slope of the roof surface, the regional climate, and the
load-bearing capacity of the underlying structure all play important roles. (Of
course, the owner's financial resources also make a difference!)

Deeper roofs (usually called "intensive" roofs)
deliver greater benefits across the board. However, they require lower slopes,
heavier structure, and more money in order to build properly. Light
"extensive" roofs provide most of the benefits of green roof construction
in a more affordable, flexible system. This makes them perfect for use on
buildings where a heavy intensive roof would not be feasible.

Green Roof Components

Regardless of its design and overall depth, every green roof
shares certain common components. The outermost layer is of course composed of
living plants. On the opposite side, protecting the roof structure, is a
waterproof membrane. The material the vegetation is planted in is known as the
growth medium, and it can be either natural soil or a synthetic alternative.
Beneath this is a drainage layer designed to capture and retain precipitation.
A root barrier is installed next to prevent the roof's plants from penetrating
the building.

Many modern green roof construction systems often combine
one or more of these layers into a modular, self-contained package. These
systems are typically designed as a series of plates, mats, or trays. Many
manufacturers even offer all-in-one modules that can be installed on an
existing roof in a single step. Although this minimizes the hassle involved in
installing a green roof, it can also be difficult to achieve strong,
long-lasting results with generic solutions like this. Most owners find that
customized designs deliver the best long-term value.

A Long Term Investment

A green roof is a costly investment, and it's not something
that a property owner should pick out on a whim. It's important to verify that
a structure is capable of supporting a green roof and that the chosen installer
can put it on properly before making any final decisions. Green roofs can cut
energy costs and lower a building's negative impact on the surrounding
environment, but they do have to be designed and installed properly for full
effect.